_Certhia_, LINNÆUS, Syst. Nat. ed. 10th, 1758, 112. (Type, _C.
familiaris_.) (See REICHENBACH, Handbuch, I, II, 1853, 256, for a
monograph of the genus.)
[Line drawing: _Certhia americana._
827 ♂]
GEN. CHAR. Plumage soft and loose. Bill as long as head, not notched,
compressed; all its lateral outlines decurved. Nostrils not overhung
by feathers, linear, with an incumbent thickened scale, as in
_Troglodytes_. No rictal bristles, and the loral and frontal feathers
smooth, without bristly shafts. Tarsus scutellate anteriorly, shorter
than middle toe, which again is shorter than hind toe. All claws very
long, much curved and compressed; outer lateral toe much the longer;
basal joint of middle toe entirely adherent to adjacent ones. Wings
rather pointed, about equal to the tail, the feathers of which are
much pointed, with stiffened shafts. Primaries ten; first less than
half the second. Nest in holes of trees; eggs white, sprinkled with
reddish.
[Illustration: _Certhia americana._]
Of the _Certhiadæ_ but one genus belongs to America,—_Certhia_, with
its one small species of considerable variability with locality. The
characters above given include both family and generic characters,
derived from this one genus. This is readily distinguished by the
decurved, compressed bill; absence of notch and bristles; exposed
linear nostrils with incumbent scales; connate middle toe, very long
claws, short tarsi, pointed and stiffened tail-feathers, etc.
The American and European varieties (they can scarcely be called
species) resemble each other very closely, though they appear to be
distinguished by such differences as the following:—
The two European races, _C. familiaris_ and _C. costæ_, both differ
from all the American varieties in having the crissum scarcely tinged
with yellowish. _C. familiaris_ is more ashy beneath than any others,
and _C. costæ_ is purest white beneath of all. Nearest _C.
familiaris_, in the American series, as regards tints of the upper
parts, are the Pacific coast specimens of _C. americana_,—while the
latter are most like the Atlantic region specimens of the same. _C.
mexicana_ is to be compared only with the North American forms, though
it is the only one approaching _familiaris_ in the ashy lower parts.
_C. familiaris_ is at once separated from the rest by having the tail
shorter than the wing.
_C. costæ_ is almost precisely like Eastern specimens of _C.
americana_ in colors, but is absolutely pure white below, and without
the distinctly yellowish crissum of the American bird. The bill and
claws, however, are considerably longer than in Eastern _americana_,
though their size is almost equalled by those of Western specimens;
the colors are, however, more decidedly different.
There is never any deviation from the generic _pattern_ of coloration;
but the variation, _among individuals of each form_, in length of the
bill and claws, as well as the tail, is remarkable.
Certhia familiaris, var. americana, BONAP.